I would take a little more, mine is 4 1/2 inches, then 1/2 inch between that and the end caps. Just watch the side trimming of your bucket, I think from memory you need to leave more on one side, think it was the left, when you put it all together you will see what I mean. I aligned the pieces by measuring from the peak of the cheek traps to the dimple of the ear screw. The bucket does sit off set so it will look weird when you first look at it